What is the best octane to run in these trucks with the 302 v8 5.0 or does it really matter?

Right now I am using 89.

 

That should be fine. Eveyonce in a while run a tank of Plus.

 

It is recommended to use 87 octane, anything more is a waste unless performance upgrades have been done to the truck. The computer is calibrated to use 87.

 

As long as it runs good on 87, than I'd run 87. I would only run the more expensive stuff if your having problems with spark knock or any problems along that line

 

i run 87 in my 89 every noe and the ill go for the higher stuff to clean her out abit

 

As long as its not pinging, there is really no reason to run anything other than 87.

 

It pings on 87 and also seems like since ethonal has been added to the gas it has made it worse and hurts my fuel mileage

BTW I have the 90 model 150xlt

 

Check the computer for codes. The knock sensor may not be working, and if it isn't the computer doesn't sense the pinging it can't adjust the timing to correct it. Make sure the spout hasn't fallen out also.

 

I use 87 octane in my 86 302 seems to work quite nicely i want to move up to 91 octane this summer if we arnt seeing ty gas prices

 

higher octane is wasted unless you are running high compression or a forced induction system such as a turbo or super charger. an octane rating is a value on the resistance to preignition due to high cylinder heat/pressure therefore running anything over the recommended 87 is just wasting money. ethanol actually has a higher octane rating than regular gas but it requires higher compression and a different fuel/air ratio to work as efficient.
so if your having spark knock in a stock engine there is something else causing problems. i would check to make sure your timing isn't over advanced.